They (Adobe) have 4 types (no-name, aka normal, etc; condensed; semi-condensed; semi-extended) and 5 styles for each type (actually 10, if we add italic version of each style: light, regular, semibold, bold, black). I have done some tests (in Corel), and, for example, Myriad Pro Light in bold will be more bold than normal Myriad Pro (regular).

EDIT: in PS, Light version forced to bold is less bold than regular/normal version. Don't forget that PS will force any font to bold, while Corel don't do that, i.e. not all fonts can be forced to bold.